The invention relates to a support system for super-insulation disposed in the annular space between concentrically arranged flexible corrugated tubes.
Such flexible corrugated tubes are used as transmission ducts for refrigerants such as liquid helium or liquid nitrogen. Another field of application relates to superconductors, which are cooled by helium, or high-temperature superconductors, which are cooled by nitrogen and are disposed in a flexible corrugated pipe.
For insulation, the corrugated tube to be insulated is wrapped with super-insulation, which is disposed in an evacuated annular gap between two corrugated tubes. In order to achieve the best possible insulation, a contact between the outer corrugated tube and the super-insulation by spacers should be avoided. From S. Yamada, T. Mits, H. Chikaraishi, S. Tanahashi, S. Kitagawa, J. Yamamoto, and O. Motojima; xe2x80x9cSuper-conducting Current Feeder System for the Large Helical Devicexe2x80x9d, presented at MT-14, Tampere, Finland, Jun. 11-16, B72, a superconductor with a spacer structure is known which consists of four intertwined plastic hoses and which is wrapped around the super-insulation for centering the inner corrugated tube within the outer corrugated tube and to eliminate a contact between the superinsulation and the outer corrugated tube. It is however, a substantial disadvantage of this arrangement, that the thermal resistance of the super-insulation is substantially reduced by being subjected to the radial pressure load exerted by the spacer structure. In rigid tubes, the super-insulation between the inner and the outer tubes is disturbed by supports arranged only at relatively large distances from one another. The quality of the super-insulation is therefore not detrimentally affected by radial loads and the relatively large heat transfer at the support locations is not a large contributing factor for the heat flow per length unit because of the large distance between the support locations. In flexible tubes, however, the distances between the support locations are smaller because of possible bends in the tubes; they depend on the minimum bend radius of the tubes.
It is the object of the present invention to provide a support system for the insulation between concentric flexible tubes which provides for a high heat flow resistance.
In a super-insulation support system disposed in an annular space between concentric inner and outer corrugated tubes, a number of axially spaced rings is provided, which are interconnected by axially extending rods mounted in circumferentially spaced relationship alternately to the inside and the outside of the axially spaced rings thereby forming a cylindrical frame structure, which is disposed adjacent the inner corrugated tube and super-insulation is disposed on the cylindrical frame structure and supported thereby at a distance from the corrugated inner tube.
With the flexible tube support arrangement according to the invention, a separation of the isolation and the support system is achieved in the relatively small gaps necessary for the centering of the corrugated tube while maintaining the minimum bend radius. In this way, the heat transfer through the support system is only relatively small because only a relatively small number of heat transfer-relevant contact locations, small contact and cross-section areas and relatively large distances between the support locations at the inner and greater corrugated tubes are provided.
Below, an embodiment of the invention will be described in greater detail on the basis of the accompanying drawings.